A conventional DC-DC converter is a synchronous buck converter, which typically has minimal components, and therefore is widely used in power supply applications. In an example application, the input voltage to a buck converter may be 12VDC. An output voltage produced by the power supply may be 5.0VDC, 3.3 VDC, or lower.
A typical configuration of a power supply such as a so-called synchronous buck converter includes an inductor, a high side switch, and a low side switch. A controller associated with the buck converter repeatedly pulses the high side switch (e.g., control switch) ON to convey power from a power source through the inductor to a dynamic load. Via a switch driver circuit, the controller repeatedly pulses the low side switch (e.g., synchronous switch) ON to provide a low impedance path from a node of the inductor to ground in order to control an output of the buck converter. Thus, the energy stored in the inductor increases during a time when the high side switch is ON and decreases during a time when the low side switch is ON. During switching operation, the inductor transfers energy from the input to the output of the converter.
FIG. 1 is an example diagram illustrating a conventional switch driver circuit 100. Conventional switch driver circuit 100 includes a series combination of a P-type field effect transistor 110-1 and an N-type field effect transistor 110-2 to drive a respective gate of a high side switch (e.g., an external switch to the switch driver circuit 100) in a power supply circuit such as a buck converter. The pull-up control signal controls a state of field effect transistor 110-1; the pull-down control signal controls a state of field effect transistor 110-2.
Activation of the P-type field effect transistor 110-1 in the driver circuit, while the N-type field effect transistor is OFF, causes the switch driver circuit 100 to drive (based on a low resistance path between the drain and source of P-type field effect transistor 110-1) a gate of the external switch to an appropriate voltage (namely, VDRIVE) to activate the external switch to an ON state. Conversely, activation of the N-type field effect transistor 110-2 while the P-type field effect transistor 110-1 is OFF causes the switch driver circuit 100 to drive a respective gate of the external switch circuitry to a low voltage to set the switch to an OFF state. Accordingly, the conventional switch driver circuit 100 is able to activate and deactivate a respective switch in a switching power supply.